1. The Field of Invention
This invention relates to a barrier designed to absorb sound produced by highway traffic. Specifically, the invention pertains to extended lengths of pultruded tubing of fiber reinforced plastic which is filled within the tube hollow with shredded, recycled thermoplastic polymers for sound absorption. An array of such tubes may be bonded to form an integral sound wall.
2. Prior Art
The expansion of major highways and other forms of ground transportation within residential areas naturally leads to intrusion of unwanted sound, which may even be detrimental to health. Government involvement in environmental control of this problem has lead to required use of sound barriers to reduce sound transmission. An ongoing challenge in this endeavor has been to develop a product that is cost effective with natural materials such as wood and concrete, but which is more easily stored, transported and installed.
U.S. Pat. No. 4,143,495 discloses the use of a sound wall constructed of elongate, sheet metal panels which contain shredded polymer material, such as recycled tires. These panels form modular segments similar to concrete panels which can be lowered into opposing slotted columns in vertical alignment to form a wall section. A similar metal panel is shown in U.S. Pat. No. 2,423,199, using a fibrous material as an internal sound absorbing medium.
Several attempts have been made by the present inventor to apply plastics technology to this need, particularly in view of the known durability of many plastic materials, their light weight and ease of storage and installation. See, for example, U.S. Pat. No. 5,217,771. This resource has been complemented with use of recycled plastics as sound absorbing filler, based on the ready availability of large volumes of refuse materials made of plastics such as polyolifins. These materials may be combined with more dense polymers such as spent tires (another refuse disposal problem of major proportion) to develop a modular sound wall structure made of extruded or pultruded plastic materials. See, for example, U.S. Pat. No. 5,272,284 by the present inventor.
None of these efforts has yielded a commercially acceptable product that maximizes the cost benefits of recycled plastics, with the use of fiber-reinforced plastic (FRP) as a load bearing, structural member.